Evolution: the Facts.

[dgilman]

"That's just a small sampling of theists who accept evolution as true."

The Dr. S Garte has his PhD in Biology. He's a theist who believes in the evolution theory in its current form. I have not said that evolution does not occur. The evidence is overwhelming. I however insist that the current theory uses way too much extrapolations that are too immense to be reasonable. The evidences available suggests things different to some of the details in the current theory.

 

[dgilman]

"There is extensive biochemical evidence that it is a trivial matter to generate self replicating molecules that take their own building blocks as substrate and then make more copies of themselves. These self replicating molecules are however far from perfect in making copies, introducing the elements needed to evolve.
RNA, or RNA-like molecules are among these, but are far from the only ones."

Read that experiment. The follow up was not posted, but was related to me by Dr. Garte. The thing ground to a halt. They were very disappointed.

"The building blocks for these molecules are produced during simple organic reactions that would/could have occurred in pre-biotic environment of earth as we understand it.
And as pointed out, many of these molecules have been found in space, showing how simple the reactions truly are and how durable those molecules in the absence of oxygen."

You need to read the thesis by Dr. Shapiro. I gave the URL above. (pnas.org/content/96/8/4396.full) NB add the tripple 'w' and the dot.

 

[Kotatsu]

The evidence is even proof to me that new species can be generated, but how far away from the ancestral taxon level it is reasonable to conclude is possible has not yet been established.

This sentence makes no sense. No ancestors of any organism -- living, dead, or theoretical -- has ever been on a different taxon level than the organism in question, if by "taxon level" you mean "taxonomic rank". All organisms have always been on the species level.

The extrapolations I read and hear are way too vast to be accepted as reasonable.

Incorrect; they may be too vast for you to accept as reasonable, but your generalization is not permissible. I, for instance, commonly find these extrapolations reasonable.

Plus the organism would have to gain, lose or fuse whole or parts of chromosomes at some stage. This has to be done with immense precision.

Not at all. Christensen's excellent 1980 book on chromosome numbers in annelid worms shows that duplication and fusion of chromosomes can happen seemingly haphazardly in worms. A higher ploidy level will lead to the species switching from a sexual mode of reproduction to an asexual one, with gradual deterioration of sexual organs, but otherwise, the organisms are morphologically identical in many cases. Note that chromosome increases are exceedingly common in annelid worms. The worm I did my Master thesis on, way back, actually has individuals in the same population that are diploid, triploid, 4-ploid, and all the way up to 11-ploid, beyond which the individual chromosomes get too closely packed in the nuclei to be countable with any degree of certainty.

It would also have to be done with very impressive efficiency to account for the rates I see in the timelines observed.

In organisms that can switch between asexual and sexual modes of reproduction, a doubling in chromosome number can occur and become fixed from one (sexual) generation to another. A great paper by Song et al. (1994) showed that allopolyploidy in mustards can result in a ca. 9% genetic difference and morphological differences (both compared to the parent plants) in at least 8 scored characters within four generations. In the same worm as above (Lumbriculus variegatus), polyploidization can result in duplication, distortion, or loss of one, several, or all genital elements from one generation to another. These are all short timelines for extensive morphological changes. Over evolutionary time, these changes has the potential to be enormous.

I conclude therefore that although mutations, natural selection, most likely in association with genetic re-sequencing do produce new species, I still hold that the evolution theory, in its current form, is still unsupported by the observations.

Am I to assume, then, that you have sufficient expertise in the matter to give a specific example, rather than treat only generalizations?

Regarding my comment on the lack of good evidence to support the belief that multi-cellular life evolved from uni-cellular life, the examples given as "intermediate forms" are not good examples. Some of those colonies aren't even of individuals of the same species.

"Some" is not an example. Give specific examples, so that your points can be understood and discussed.

Those that are are still unique individuals with differing DNA whereas the multi-cellular units are not and all have the same DNA.

If this were true, it would have been impossible to sequence extant colonial organisms in which it is hard or impossible to isolate zooids for DNA extraction. This is not the case. Hydroids, bryozoans, coral, and other colonial organisms that are clonal have the same DNA, and a large sample of a given colony can be extracted without running the risk of having multiple genotypes in the same vial.

But please present specific example to the contrary. As evidenced by my list in the previous post, I do not possess intimate knowledge of more than a few select groups of animals, and may certainly have missed some.

The difficulty not explained nor confirmed is how the gonads were modified to produce individuals whose cells would remain attached and modify themselves to become the various tissues.

The gonads need not be involved in any way in colonial growth, if this growth is clonal. Parthenogenesis is well evidenced throughout the Metazoa, and does not require even the existence of gonads.

There is therefore no scientific basis, only immense extrapolations, unconfirmed and nu-corroborated. The best examples of those colonies are all called "pseudo-tissues" by my biologist friend.

Statements such as this will have to be assumed to be made up until you can provide specific examples of the organisms you refer to.

 

[Lukraak_Sisser]

"Great! A biologist. The observation do indicate that natural selection exists; that is indisputable. The evidence is even proof to me that new species can be generated, but how far away from the ancestral taxon level it is reasonable to conclude is possible has not yet been established. The extrapolations I read and hear are way too vast to be accepted as reasonable. Plus the organism would have to gain, lose or fuse whole or parts of chromosomes at some stage. This has to be done with immense precision.

It would also have to be done with very impressive efficiency to account for the rates I see in the timelines observed. I conclude therefore that although mutations, natural selection, most likely in association with genetic re-sequencing do produce new species, I still hold that the evolution theory, in its current form, is still unsupported by the observations.

Read up on genome duplication sometimes. What you suggest is neither uncommon nor unobserved. And once a genome has been duplicated there is a whole genome of redundant genes that can mutate with a lot less constraints, rapidly (geologically speaking) leading to diversification of species.

Regarding my comment on the lack of good evidence to support the belief that multi-cellular life evolved from uni-cellular life, the examples given as "intermediate forms" are not good examples. Some of those colonies aren't even of individuals of the same species. Those that are are still unique individuals with differing DNA whereas the multi-cellular units are not and all have the same DNA. The difficulty not explained nor confirmed is how the gonads were modified to produce individuals whose cells would remain attached and modify themselves to become the various tissues. There is therefore no scientific basis, only immense extrapolations, unconfirmed and nu-corroborated. The best examples of those colonies are all called "pseudo-tissues" by my biologist friend.

"What is scientific evidence for you? A lot of scientific knowledge is based on inference, and I find it curious why you should exclude it here."

What you seem to keep excluding that it is interference based on observations and experiments, which is more than can be said from ID/creationism, unless you can point to an experiment in which a creation de novo took place.
They assume the same as the scientists they decry, except they go back even further. Their assumtion is that before the universe even existed a fully fledged omnipotent sentient being suddenly appears. At least abiogenesis theories as currently supported do not need such an immense leap of unconfirmed supposition.

The inferences do not all fit well or are often contradicted by other observations. Gradualism is contradicted by the observations in the Tommotian layers, yet it hasn't been abandoned and "punctuated equilibrium" remains unsupported by actual evidence and requires the use of circular logic to maintain.

Yet all of this is at least better supported by data than anything put forward by the ID/creationism crowd. Just because a theory is difficult to prove and has parts that still need clearing up does not mean it should be replaced by something based on wishful thinking and no evidence whatsoever.
I don't understand quantum mechanics myself. If I now theorize that actually my GPS works because fairies tell it where it is located, would you accept that theory? Or would you go with the theories that led to actually building a GPS system?
If the latter, then why go for an unfounded theory over the one that has consitantly yielded predictable results and various forms of medicine?

 

[Lukraak_Sisser]

"There is extensive biochemical evidence that it is a trivial matter to generate self replicating molecules that take their own building blocks as substrate and then make more copies of themselves. These self replicating molecules are however far from perfect in making copies, introducing the elements needed to evolve.
RNA, or RNA-like molecules are among these, but are far from the only ones."

Read that experiment. The follow up was not posted, but was related to me by Dr. Garte. The thing ground to a halt. They were very disappointed.

"The building blocks for these molecules are produced during simple organic reactions that would/could have occurred in pre-biotic environment of earth as we understand it.
And as pointed out, many of these molecules have been found in space, showing how simple the reactions truly are and how durable those molecules in the absence of oxygen."

You need to read the thesis by Dr. Shapiro. I gave the URL above. (pnas.org/content/96/8/4396.full) NB add the tripple 'w' and the dot.

Is either of that more recent than 2 years old? Because that was the last time I worked in the RNA field in conjuction with organic chemists that were busy on the projects to synthezise RNA molecules trough non-biological reactions.
The self replicating RNA molecule field has produced more than a single study. A quick pubmed search yields 256 hits on Self replicating RNA, the most recent one being published this year. Hardly a field that has ground to a halt.

 

[Dinwar]

No there isn't. I've read the conjectures, but they do not stand up under experimentation. Even Dawkins has admitted that there are no good theories on abiogenesis. So far, it remain a belief unsupported by any scientific evidence.

To clarrify one of the more annoying things in the anti-evolution world: Dawkins is not, in any way, a god among scientists. He's good, don't get me wrong, but people disagree with him all the time. His knowledge of the fossil record, for example, leaves much to be desired. He's a biology, and therefore much less likely to know the current state of abiogenesis than, say, someone studying abiogenesis. Everything he studies lives in a world rich in oxygen, with well-established food chains and ecologies, etc.--a world as different from the Hadean Earth as it is from Jupiter.

As for the undefined reading you've done, I've done other reading and it states otherwise. How do you propose we resolve this issue?

The evidence is even proof to me that new species can be generated, but how far away from the ancestral taxon level it is reasonable to conclude is possible has not yet been established.

See, this is where I step in. I've got a book back home that outlines the evolution of vertebrates, from the little skull-less worm thing in the Cambrian to us. We have the evolution of Phylum Chordata pretty well established. I've seen works on the evolution of Arthropoda, Molluska, Bryozoa, Brachiopoda (way way WAY too much on Brachiopoda--Ohio paleontology is a tad biased towards that phylum), I've got a good friend working on Echinodermata, Antrhozoa, and other phyla. We know the evolutionary pathways reasonably well from the species level to the phylum level--BY EXAMINATION OF ACTUAL SPECIMENS.

Now, I'll grant you that we don't have a whole lot of fossils for the evolution of each phyla. However, given that each taxonomic group below phyla, to my knowledge without exception (with the caveat that any group "Indeterminant" or "Problematica" should be treated as the junk heaps of things that couldn't be placed anywhere else that they are), have all evolved the same way (subgroups split off the main group, experience evolutionoary radiation, and a few of those things survive), it's a pretty safe bet that the phyla evolved in exactly the same way.

Let's take Mammalia as an example. As a whole, Mammalia evolved from a group of therapsis with heterdont dentation and a unique jaw structure. However, any number of other heterdont therapsids were meandering about the Paleozoic world, and reptiles of the time had developed a few different jaw structures. The line that would become mammals and the line that would become dinosaurs had already split; however, if you saw the critters you would be amazed at how similar they look. I have, and that's what always strikes me.

Moving down the taxonomic scale, we have the split between Canidae and Felidae, the two groups of carnivorous placental mammals. On the Canidae side you have dogs, bears, foxes, etc. On the Felidae side you have cats, lions, tigers, some really weird extinct forms, etc. However, when these lineages first diverged (Eocene I think; may be Paleocene, but there's remarkalby little work done on that time period) both looked almost identical--and both looked more like a weasle than any cat or dog you've ever seen. Certainly not like a bear!

I could go on, but if you type in "Falsifying Phylogeny" in YouTube you'll come to AronRa's video series on the topic. It's extremely good, and if you're going to use these lines of argument you should at least watch them to see what your opponents are saying. At any rate, AronRa shows that this works from the highest taxonomic ranking to the lowest.

So, since every single example we have of the rise of a new taxonomic group boils down to an ancient speciation event with the exception of phyla, and we know that the phyla diverged prior to the evolution of readily-preservable anotomical features such as skeletons or shells, it's reasonable to conclude that phyla originated via speciation events deep in the past. In fact, I would argue that it's unreasonable to argue otherwise, at least until evidence can be presented that phyla are somehow different, fundamentally, from the rest of the taxonomic ranks.

There's been a LOT of debate on this topic, particularly with the rise of phylogenetics and cladistics. Thirty or fourty years of debate among extremely knowledgeable researchers hasn't shown any difference between how phyla are formed vs. how any other taxonomic rank are formed, at least not if you accept that taxonomy has to reflect the history of a lineage (if you don't, than phyla can represent bauplans; however, at that point you've abandoned any attempt to make your taxonomy mean anything other than which drawer to put your specimens in).

Plus the organism would have to gain, lose or fuse whole or parts of chromosomes at some stage. This has to be done with immense precision.

This isn't uncommon, and demonstrates your biase to Kingdom Animalia. Plants add genomes wholesale--it's how we get hybrids. Bacteria frequently have TWO genomes: the main DNA strand, and plasmids, the latter of which is extremely mobile. And there are any number of errors that can occur in mitosis/miosis that result in gene or chromosome duplication within a cell, and which are extremely common (in the sense that any organism's genome includes a number of them--on a per-nucleotide basis they're pretty rare, but anything times ten to the nineth becomes significant).

Those that are are still unique individuals with differing DNA whereas the multi-cellular units are not and all have the same DNA.

Your complaint about my intermediate forms is that they include both primative and derived features? REALLY?! I suggest you look up what "intermediate form" means. And don't assume that all of your cells have the same DNA--they don't.

The difficulty not explained nor confirmed is how the gonads were modified to produce individuals whose cells would remain attached and modify themselves to become the various tissues.

I never attempted to do so. I'll leave that to those better-versed in the squishy stuff than I am. However, I must again point out that wherever we have fossil evidence for any taxonomic division it universally points to the same generalized pattern, and it universally starts with speciation. Simply saying "We don't have the physical evidence" is not a counter-argument to the argument that higher taxonomic divisions likely happened the same way--you need to demonstrate that higher taxonomic divisions cannot occur the same way, that there is some fundamental aspect of life that creates a barrier to such an event (remembering that the life we're dealing with is not current life, but much more ancient and extremely alien to what you see around you today). That, or this all boils down to special pleading.

Gradualism is contradicted by the observations in the Tommotian layers, yet it hasn't been abandoned

Gradualism is a stratigraphic term, and it has--the current paradigm is Neo-Catastraphism. As far as evolution goes, the idea of slow, steady changes accumulating through time has more or less been abandoned except in special cases where specific mechanisms allow for such slow, stead accumulation (ie, molecular clocks). Evolution is far more complicated than that.

and "punctuated equilibrium" remains unsupported by actual evidence and requires the use of circular logic to maintain.

Whoever told you this is a flat-out liar. There's no other word for it. Gould and Eldredge put this to the test using a single stratigraphic section and mollusks found within it. They found that in that section you did in fact find a single ancestor which radiated into numerous decendants, only some of which survived to the end of the section. The radiation of mammals, birds, mollusks in general, Animalia in general--it all follows this pattern when you look at the rocks. Some taxa do not--Foraminifera, for example, show a phyletic gradualistic pattern of evolution. This doesn't disprove either concept, however; it merely shows that evolution is complicated, and that different conditions determine different tempos of evolution.

I would generally be skeptical about the statements biologists make about ancient critters (no offense intended, Kotatsu--I'm HIGHLY skeptical about statements paleontologists make about living ones, if that's any consolation). They study animals, plants, fungi, etc.; they do not study rocks and fossils. When you're talking about testing the tempo of evolution, you're talking about the fossil record, and a biologist is as likely to have a good understanding of that as they are to have a good understanding of quantum mechanics, and for exactly the same reason: they don't study it.

Furthermore, if you want to know the controversies of a field talk to someone in the field. As far as I can see, punctuated equilibrium is more or less seen as one of a number of tempos for evolution by most paleontologists. Some go overboard, and try to say it's THE tempo, but most are sober enough in their assessment to conclude that there's no theoretical basis for stating that any one tempo is preferable to another universally. The question now is finding what organisms follow the PE model, and which the PG.

I strongly suggest you pick up some of Steven J. Gould's works, some of Peter Ward's, and if you can find it "On the Origin of Phyla" by Valentine. Gould and Ward write popular press books which are available on Amazon.com for $5 or less each (if you know how to use Amazon.com), and explain the evidence for large-scale evolution quite well. "On the Origin of Phyla" is going to be much harder to track down, and MUCH harder to read, but it's well worth it. Valentine outlines the evidence for the origin of each phyla of animal, including both biological and paleontological data; the style is equally informative, though, as he wrote for experts in the field. It will give you a much clearer glimps into the world you're talking about. Finally, if you can get ahold of one of Shipman's works on taphonomy it'd be worth reading. Taphonomy is the study of how things move from the biosphere to the lithosphere, and is critical to understanding paleontology, which means it's critical for understanding the evolution of anything above, say, the genus level.

 

[Dinwar]

The gonads need not be involved in any way in colonial growth, if this growth is clonal. Parthenogenesis is well evidenced throughout the Metazoa, and does not require even the existence of gonads.

I recall something about bryozoa colonies having individual members that are specialized to individual tasks--and reproduction is one of them. Some capture food, some walk, some produce gamites. It's perfectlyl analogous to unicellular organisms becoming multicellular; the only difference is that the "cells" of this new superorganism are what we'd typically classify as individual organisms.

Here's a Google book on the subject. It's not the full book, but enough to demonstrate that these intermediate forms do in fact exist. I'm looking at page 3-4, Section 1.1.2.

So yes, such intermediate forms between individual organisms, collonial organisms, and superorganisms exist. The evolution of sexual organs is not that difficult, it turns out. And if there's a nuclear war bryozoans will likely be fighting with cockroaches for dominance. My money's on the bryozoans, as they have a MUCH better buit-in sheild.

 

[Kotatsu]

I've got a book back home that outlines the evolution of vertebrates, from the little skull-less worm thing in the Cambrian to us.

What, in your opinion, would be the best book on vertebrate paleontology that is at least largely accessible to a non-palaeontologist who does have a biology training?

I would generally be skeptical about the statements biologists make about ancient critters (no offense intended, Kotatsu--I'm HIGHLY skeptical about statements paleontologists make about living ones, if that's any consolation).

No worries; I wish I knew more palaeontology. I have never understood why in a natural history museum, it is perfectly acceptable to have both palaeontologists and biologists working in the same place, but this so rarely -- in my experience -- happens in universities. Granted, the geology department is just ten minutes walk from where I sit, but I don't even know if they do palaeontology or not. They do a lot of petrology, I understand, but the division between their department and ours is so complete that I have no idea. There are no courses in palaeontology offered at my university, to my knowledge, although the basic courses in biology does include some palaeontology in the lectures (but basically as a spring board for discussions of evolution).

and if you can find it "On the Origin of Phyla" by Valentine
"On the Origin of Phyla" is going to be much harder to track down, and MUCH harder to read, but it's well worth it.

The Valentine book is available in multiple copies through Amazon.co.uk:
http://www.amazon.co.uk/On-Origin-P...=sr_1_1?s=books&ie=UTF8&qid=1331659757&sr=1-1

Doesn't fit into my budget this month, but probably next month...

I recall something about bryozoa colonies having individual members that are specialized to individual tasks--and reproduction is one of them. Some capture food, some walk, some produce gamites. It's perfectlyl analogous to unicellular organisms becoming multicellular; the only difference is that the "cells" of this new superorganism are what we'd typically classify as individual organisms.

This is by no means limited to Bryozoans; some hydroids do the same as do, of course, many kinds of colonial insects (although they are perhaps not comparable as they move around freely). I believe it is found in other phyla as well, but I can't recall any specific examples at the moment. Of course, the Bryozoa also include non-colonial species, thus having the whole spectrum from non-colonial over colonial-but-identical to colonial-but-differentiated. same with the Hydrozoa, I think.

I vaguely recall from Botany class ages ago that the same is seen in some plants, like Volvox, which is initially unicellular, but which grows clonally and eventually develop cells that perform certain tasks, like reproduction, but I may be mixing things up. The Myxomycetes can move around as individual cells but also form multi-cellular structures with differentiated tasks for different cells, such that some are even "sacrificed" as stems for spore propagation structures (this again from that half-remembered botany class, so I may be mixing things up).

The next step, I understand, in the supercolonies of ants, where different anthills cooperate. I was told there is a single supercolony of an invasive ant that covers most of southern Spain and Portugal at a conference a while ago, but have never checked this so it may be wrong.

 

[Lowpro]

I vaguely recall from Botany class ages ago that the same is seen in some plants, like Volvox, which is initially unicellular, but which grows clonally and eventually develop cells that perform certain tasks, like reproduction, but I may be mixing things up. The Myxomycetes can move around as individual cells but also form multi-cellular structures with differentiated tasks for different cells, such that some are even "sacrificed" as stems for spore propagation structures (this again from that half-remembered botany class, so I may be mixing things up).

The next step, I understand, in the supercolonies of ants, where different anthills cooperate. I was told there is a single supercolony of an invasive ant that covers most of southern Spain and Portugal at a conference a while ago, but have never checked this so it may be wrong.

There was also a recent Science article about single cell yeast "evolving" into a multicellular colony with specialized cells performing particular tasks. The question became "Did it evolve that, or were the genes always there and the stresses induced selected for those genes"

http://www.pnas.org/content/109/5/1595

 

[Dinwar]

What, in your opinion, would be the best book on vertebrate paleontology that is at least largely accessible to a non-palaeontologist who does have a biology training?

Vertebrate Paleontology and Evolution is the best overall review I've seen. The terms will bog you down a bit if you're not familiar with them (they certainly do for me!), and it's an overview of the best-studied phyla so it glosses over a lot in each taxa; however, it provides good details on the important finds the important concepts in vertebrate evolution, and has page after page after page after page of references if you want to know more. The main issue is getting the names of all the taxa straight in your head, which won't be too big of an issue to a taxonomist, and understanding the names of the bumps and ridges and grooves in bones, which is a pain in the backside.

The Dinosauria is the best book on dinosaur evolution, including an introduction to birds (something you may find particularly interesting, given your research). Right now it's one of my prized posessions. EXTREMELY detailed--this isn't a book to sit down and read through, but rather a reference book so information dense it warps space-time. This approach is extremely valuable, however, because it's exactly those details that show evolutionary histories. And the authors are aware of this. Each chapter is broken up into skull/jaw anatomy, postcraneal anatomy, evolutionary history, ecology, paleogeography, etc., all in the same order so the individual taxa are easily compared with one another. The paleogeography part is valueable for my work, because it provides a quick-and-dirty assesment of which strata are most likely to yeild fossils.

A bit ethnocentric, but The Evolution of Tertiary mammals of North America has a lot going for it--it's basically The Dinosauria for North American mammals. I'm trying to convince my wife that it's worth spending $300 on reference material right now.

Life History of a Fossil is a most-read in my opinion. While taphonomy has certainly moved past this one volume, Shipman is very good at providing both a theoretical and practical background for the study. And since all of paleontology is impacted by taphonomy, knowing a bit about it helps. Particularly when you look at small critters, it turns out...

Two other books I should recommend: Principles of Sedimentology and Stratigraphy, and Isotopes: Principles and Applications. I'll confess to a bit of heresy here: I'm not an anatomist, like most paleontologists are. I'm more a paleoecologist, and take the view that learning the fossils without knowing about the rocks is akin to learning all of the letters in The Lord of the Rings but not learning the plot. Neither book directly deals with vertebrate evolution, but they give you the tools to put any finds into their proper geologic context.

All links go to Amazon.com, to the books in question.

I don't really have any good references on fish or non-dinosaur lizards or birds, other than that first textbook. They simply haven't come across my radar--other than a brief mention of lizards in the La Brea Tar Pits, California paleontology doesn't spend much time on either so I haven't had a chance to look into them.

Doesn't fit into my budget this month, but probably next month...

Yeah, that's the thing--this stuff ain't cheap. It requires a lot of work to put together (The Dinosauria took something like a decade, with multiple researchers), and the end product is only of interest to a small niche audience. Micropublishing has helped some, but it's still not something you can do on a whim. As I said in another thread, science has a pretty high cost of entry. $100 for a book isn't actually that bad. Though I'd HIGHLY recommend getting the books used if possible. For two reasons: first, it's cheaper, and second, the marginalia in the books can be as informative and frankly fun as the data in the books themselves.

I have never understood why in a natural history museum, it is perfectly acceptable to have both palaeontologists and biologists working in the same place, but this so rarely -- in my experience -- happens in universities.

The history of the dicipline. Paleontology basically stalled out for a hundred years or so, and the only really interesting work was done by micropaleontologists working with oil companies. The rest was limited to dry-as-dust morphology descriptions. So you got a situation where a lot of the paleontological work was being done alongside a lot of petrology, sedimentology, and drilling--all of which are geologic persuits. There's also the fact that the guys who founded paleontology also founded geology, so there's a strong affinity between the groups. Oddly enough, paleontologists are also isolated from their geologic cohorts as well as biologists--most paleontologists don't actually know much about sedimentology, which has caused no small portion of the forehead-shaped dent in my desk (and once, while reading Shipmans work, caused me to wake my wife up because I was reading in bed and started laughing histarically).

This is by no means limited to Bryozoans; some hydroids do the same as do, of course, many kinds of colonial insects (although they are perhaps not comparable as they move around freely).

Yeah, that's why I didn't bring them up. You're right, though--there's really no difference in differentiation in colonial organisms that are sesile vs. those that are mobile.

I've heard of a few supercolonies of ants. Fireants in the Americas have one, that's larger than most human countries. I think this is one of those areas where the question "What is an organism?" gets fuzzy. Do we count a colony as a single organism, in which case it's a multi-individual organism? Or do we count it as a huge number of organisms, only one of which reproduces? It impacts our own taxa as well: naked mole rats are a collonial mammal.

 

[Dinwar]

If you want to go old-school, try this one out. A word of caution, though: Owen was known to be....well, an arogant jerk who didn't listen to anything anyone else had to say. A very good anatomist, but he did falsify his work on apes to fit his a priory convinctions (it has to be said, they were religiously based). Still, this serves as one of the classic texts on the subject of vertebrate anatomy, which is central to vertebrate paleontology.

 

[jimbob]

Thanks Dinwar and Koatsu and Lukraak_Sisser

 

[Kotatsu]

There was also a recent Science article about single cell yeast "evolving" into a multicellular colony with specialized cells performing particular tasks. The question became "Did it evolve that, or were the genes always there and the stresses induced selected for those genes"

http://www.pnas.org/content/109/5/1595

This is very cool! Haven't read the article yet, but thank you!

All links go to Amazon.com, to the books in question.

Thank you for these recommendations. The only more scholarly (1) book on palaeontology I ever read was Evolution and Extinction of Dinosaurs by Fastovsky and Weishampel, which I found was a good introduction. I was also given this book ("Age of Dinosaurs in Russia and Mongolia" for free at a book fair a few years ago, but never read it... as I understand it, it's a bunch of translations into English of old Soviet articles on palaeontology. Seeing the price of the book now (85 pounds!), I conclude that it is often good to visit book fairs on the last day when foreign publishers just want to get rid of stuff and are willing to give you thick books for free.

After I finish and defend my thesis next month, I will have loads of time as an unemployed looking-for-post-doc-grants systematist and taxonomist, so I will get some of these books and broaden my biological knowledge.

What I'd really like to know more about, though, are those ancient crocodiles and the jawless sharks and so on that lived before the dinosaurs. It seems most textbooks on evolutionary history I come across skip straight from the Cambrian explosion to the age of dinosaurs, mentioning things like Trilobites and Orthoceratites and so on only in passing, and then move on to how dinosaurs became birds, leaving the impression that mammals evolved from animals that were not interesting enough to get into the book. Being a collector of plastic dinosaurs (2), I recently found and got this, a set of "prehistoric crocodiles", which just increased my unfulfilled interest in these animals.

Yeah, that's the thing--this stuff ain't cheap.

Still, 30 pounds or 30 dollars -- which is the second hand price of some of the books you linked to -- isn't that much, really. I paid as much for "The Chewing Lice -- World Checklist and Biological Overview", and definitely spend that much on SF every now and then... so I should just change my book-buying algorithm from getting yet another Haika Soru book to get something that I can actually use...

I've heard of a few supercolonies of ants. Fireants in the Americas have one, that's larger than most human countries. I think this is one of those areas where the question "What is an organism?" gets fuzzy. Do we count a colony as a single organism, in which case it's a multi-individual organism? Or do we count it as a huge number of organisms, only one of which reproduces? It impacts our own taxa as well: naked mole rats are a collonial mammal.

I unfortunately know too little about this kind of thing, but I do find ants fascinating. I'm definitely torn on the issue, but leans towards thinking that evolutionarily, it only makes sense to consider the actually reproducing individuals as actual organisms, and the others being extensions or organs of that organism that just happen to be separated from it. Sort of like how we wouldn't treat a dropped feather as a distinct organism from the bird that dropped it, just because it has become detached (a somewhat flawed analogy, I guess, but still...)

However, I recognise that this approach certainly has huge problems of its own, especially if you want to be consistent throughout the Metazoa. I personally don't think there is any reason to be consistent about these things on such a large scale for any concept, and would be perfectly content to say that "individual" or "organism" means X in these phyla, and Y in these phyla, similar to how "species" necessarily must be treated as vastly different concepts in different organism groups. It makes no sense to argue that "species", "genus", "individual", "organism" or "population" should mean the same in two randomly selected groups of ... um... organisms.

In the case of organisms where each discrete entity can potentially reproduce, it makes sense to apply one standard, but in any form of colonial organism, it makes perfect sense to apply a different standard. In asexually reproducing organisms, perhaps a third standard is reasonable, depending on exactly how those organisms are reproducing asexually. In the cases of the sea bass that are all female and require the sperm of a different species of sea bass in order to initiate ovulation (even if the sperm just dissolves and is used as nutrients rather than contributing in a genetic way to the next generation), it may make sense to apply the same standard as in sexual, non-colonial organisms. On the other hand, in annelids like Lumbriculus, where every segment can potentially regenerate a new (??? at least a separate) individual, the same standard may make no sense, and these worms may be theoretically immortal.

But then again, most generalisations break down once you start looking as asexual organisms... Just imagine how different biology would have been if humans had been asexual!

---
(1) Though I've read no end of kids' books on dinosaurs when I was younger, of course, as well as a book that proves CONCLUSIVELY (so the cover says) that Jesus walked among dinosaurs. It even has artist's impressions of the event, so I gather it must be true.
(2) One of my cats recently bit off the tip of the tail of my Invicta Baryonyx!!!! I was so mad at him, but he didn't understand what I was saying, and just ran away to push down a plant or chew a cable or something.

 

[Dinwar]

Yeah, crocs don't get much love. It's actually somewhat problematic, because crock teeth and spinosaurus teeth are extremely similar, and the fact that no one cares about crocs means that a LOT of teeth get misidentified.

The first book I linked to includes some good data on pretty much all the major vertebrate groups, including jawless fish, sharks, amphibians (you want to talk about weird--the first land vertebrates make the dinosaurs look normal, and were HUGE compared to modern amphibians!), and crocs. It doesn't get into the fine-scale details--it's not going to give an osteological analysis for each genus, for example--but it'll give you a good picture of what we know (well, knew--it's a textbook, what can you do?). It'll also give you the names of people to look up. The fact that the authors cite pretty much everything they could get their hands on means that you can quickly get a sense of who the major players are.

Another guy you may want to look into is Peter Ward. He's mostly worked on the Permo-Triassic boundary, and did a lot of work with gorgons (mammal-like reptiles that pretty much disapeared at the end of the Permian). He's got some books written for popular audiences, but I've also cited a number of his papers on ammonites, back when he was working on the K/Pg event.

Also, I may have found my nephiews' holiday presents. May as well start early, right?

Still, 30 pounds or 30 dollars -- which is the second hand price of some of the books you linked to -- isn't that much, really.

True, and if you wait you can sometimes pick the volumes up even cheaper. Like I said, I don't mind if there's some stuff written in the margins--sometimes that's as useful as the stuff in the books themselves (most of mine have minor corrections, updates, etc. in the margins). The Tertiary mammal one is expensive enough to be problematic, as a few of the reviews indicate. Not sure how much a crock book would cost, to be honest. I'm sure they're out there, but I've never actually seen any.

'm definitely torn on the issue, but leans towards thinking that evolutionarily, it only makes sense to consider the actually reproducing individuals as actual organisms, and the others being extensions or organs of that organism that just happen to be separated from it. Sort of like how we wouldn't treat a dropped feather as a distinct organism from the bird that dropped it, just because it has become detached (a somewhat flawed analogy, I guess, but still...)

That's my view, mostly. If you try to apply evolutionary mathematics (Hardy/Weinburg or something) to ants, bees, or naked mole rats you have to apply them to the queens and drones. There is one difference, though: the ants operate under the concept of kin selection, and while I'm sure that's part of how an organism goes from unicellular to multicellular I'm not convinced that's all. I mean, you can't say that kin selection explains why my hands exist, despite the fact that from an evolutionary perspective my body is merely a machine to care for and utilize my genetals (not a nice way to look at things, but it's also not entirely invalid). Then again, ants, bees, et al. represent just about the most extreme kin selection possible. I don't know--like you said, concepts tend to break down once you get past simple sexually reproducing species.

I'm reading "Engineers of Ringworld" just now, and one of the species reproduces by the male and female injecting sperm and eggs into a host--the character states that as far as its species is concerned, there are two types of male and the female is another species entirely. Weird, but really not uncommon, and it'd give us a whole new perspective on taxonomy.

I do like your idea that we shouldn't attempt to apply standards universally. The standards are based on biology, and when the biology gets to be different enough it all breaks down. Which makes sense--the concept of "eating" breaks down as well, as does "reproduction" (plants have alternating generations, bacteria simply split, sponges can reproduce from a piece breaking off, etc). It makes sense the the concept of species should be different in different groups. It may be interesting to see if that's a useful characteristic in terms of taxonomy--it's pretty fundamental, and should be relatively conservative I would think (meaning that you wouldn't get too many throw-backs). Only problem would be that some types of species may arise independantly in multiple lineages, but we deal with that now anyway so it's not a major hurddle.

 

[jimbob]

I'd say that natural selection acts on the scale of the replicating unit, be that genes within cells (cf cancer) or the organism itself.

 

[Kotatsu]

It makes sense the the concept of species should be different in different groups.

A quick note before I leave for work:
The funny thing is that perhaps "species" needn't be different for different groups, as long as you use a unified species concept and realize that all species concepts are looking at "species" the wrong way. This is taken mainly from what I remember of a paper I read ages ago (de Queiroz? 2005?), which basically said that all the various species concepts divide populations in ways that we would expect if speciation was instantaneous and always complete. Then we would expect reproductive incompatibility and different niches and so on. However, speciation is typically a progress that occurs over long time spans, and there is no reason to assume that the end results of this process will all follow the same succession in all lineages. I can't remember what the conclusion was, however, so I'll have to dig up that paper again and have a look.

 

[Sideroxylon]

A quick note before I leave for work:
The funny thing is that perhaps "species" needn't be different for different groups, as long as you use a unified species concept and realize that all species concepts are looking at "species" the wrong way. This is taken mainly from what I remember of a paper I read ages ago (de Queiroz? 2005?), which basically said that all the various species concepts divide populations in ways that we would expect if speciation was instantaneous and always complete. Then we would expect reproductive incompatibility and different niches and so on. However, speciation is typically a progress that occurs over long time spans, and there is no reason to assume that the end results of this process will all follow the same succession in all lineages. I can't remember what the conclusion was, however, so I'll have to dig up that paper again and have a look.

Would love a link or summary if you do locate it.

 

[Kotatsu]

Would love a link or summary if you do locate it.

I am about to run away to teach, but I could send you a pdf even, if I can figure out which paper it is I am referring to. I recall there are even two similar proposals, which were compared and reviewed in a recent paper, and I'll see if I can find all of them.

 

[Dinwar]

I've often wondered if we shouldn't discuss populations, rather than species. The population is, after all, the unit of evolution (an individual doesn't evolve, and a species as such doesn't evolve--the population changes over time). It would clear up a lot (but certainly not all) of the ambiguity with the species concept. For example, two organisms are considered (by the biological species concept) to be the same species if they can potentially interbreed. They're the same population if they're both part of the group that actually interbreeds (this sentence is very sloppy, but I think it gets my point across). There's have to be some limit, and some other rules--a single member of a population breeding with a single member of another population does not mean that those two are the same population, and ring species play merry havoc with pretty much any definition of anything--but it would remove some of the more silly consequences of the term "species".

Of course, the REAL problem is that we're trying to apply a somewhat rigid framework to what is by its nature an extremely fluid concept. Where you draw the line is always going to be a bit arbitrary, and there's always going to be viable arguments to be made that the line should be HERE, not THERE.

 

[Sideroxylon]

I have read that in some definitions of species that the actual practice, rather than potential to breed and produce reproductively viable offspring is the criteria. I understand that there are some animals (I recall some grasshoppers) that can potentially mate but do not.

How do you define a population? Can that also be a problematic definition?